Dispersion of the nonlinear optical susceptibility tensor in centrosymmetric media

The production of light at the combination frequency 2₁-₂ in centrosymmetric media has been observed as a function of the frequencies ₁ and ₂ and the polarization directions of two incident dye-laser beams. The interference of the Raman resonance with the complex electronic contribution to ^ (3) has been observed. In diamond and in benzene all of the components of the third-order nonlinear susceptibility have been measured and calibrated with respect to known cross sections for spontaneous Raman emission. Contributions to the cubic nonlinearity have also been measured in the fluoride series CaF₂, SrF₂, CdF₂, BaF₂, and in calcite.